The cross-linked modified organopolysiloxanes obtained from the present process are more transparent and/or are much more rigid than the products which have been obtained heretofore from the processes described in the prior art. The improved properties are achieved primarily by polymerizing monomers containing aliphatic multiple bonds in the presence of organopolysiloxanes containing at least 40 mol percent of mono-organosiloxane units, but simultaneously in the presence of a condensation catalyst for the organopolysiloxane, or in the presence of a catalyst which promotes the addition of Si-bonded hydrogen to Si-bonded alkenyl groups.
German Pat. No. 1,957,356, refers to the reaction of condensable groups of a condensable organopolysiloxane with an acrylester having alcoholic hydroxyl groups and the polymerization of vinyl monomers in the presence of the acryl-siloxane-resin thus obtained. Compared to this process, the process of this invention offers at the very least the advantage that it is far less expensive. U.S. Pat. No. 2,958,707 refers to the polymerization of at least one monomer containing at least one aliphatic multiple bond in the presence of free radicals and at least one organopolysiloxane, in which the organopolysiloxane may contain at least 40 mol percent of mono-organopolysiloxane units and condensable groups which are Si-bonded hydroxyl groups and/or alkoxy groups having from 1 to 3 carbon atoms. In this patent, acrylamide is disclosed as one of the monomers containing aliphatic multiple bonds. However none of the examples of U.S. Pat. No. 2,958,707 describe the preparation of a product having measurable rigidity. Also, German Pat. No. 968,056, describes a process for the preparation of molded objects and coatings in which polymerization products are obtained from monomers of unsaturated polymerizable hydrocarbon compounds and low-polymer silicones and are molded and hardened, i.e. cross-linked, at an elevated temperature. Because of the low ratio of methyl magnesium chloride to silicon tetrachloride present during the preparation of the organopolysiloxanes used pursuant to Example 1 of German Pat. No. 968,056, it can be assumed even in contrast to the cited formula at page 1 of said German Patent, that the organopolysiloxane also contains at least 40 mol percent of mono-organosiloxane units. Compared to the products which presumably can be obtained in accordance with the teachings of the German Patent, the products which can be obtained in accordance with the process of this invention are more transparent and/or more rigid than the products described in the prior art.
It is therefore an object of this invention to provide cross-linked, modified organopolysiloxanes having improved transparency. Another object of this invention is to provide cross-linked, modified organopolysiloxanes having improved strength and rigidity. Still another object of this invention is to provide a process for preparing cross-linked, modified organopolysiloxanes having improved rigidity and transparency. A further object of this invention is to provide a process for preparing modified organopolysiloxanes by polymerizing a monomer having an aliphatic multiple bond in the presence of a cross-linked organopolysiloxane. A still further object of this invention is to provide a process for preparing modified organopolysiloxanes by simultaneously cross-linking an organopolysiloxane while polymerizing a monomer having an aliphatic multiple bond.